JP2012190663A - Dye-sensitized photoelectric conversion element and manufacturing method of dye-sensitized photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye-sensitized photoelectric conversion element capable of improving photoelectric conversion efficiency and allowing production even by performing low temperature firing, and to provide a manufacturing method of the dye-sensitized photoelectric conversion element.SOLUTION: A semiconductor fine particle layer on which a dye is carried is provided for a dye-sensitized semiconductor layer 2. The semiconductor fine particle layer includes a metal oxide semiconductor fine particles and an insulating layer which covers at least a part of a surface of the metal oxide semiconductor fine particles, and the insulating layer includes a metal oxide having an amorphous phase at least in a part thereof.

Description

  The present technology relates to a dye-sensitized photoelectric conversion element and a method for producing the dye-sensitized photoelectric conversion element, and is applied to, for example, a dye-sensitized solar cell using a dye-sensitized semiconductor layer including semiconductor fine particles supporting a dye. Is preferred.

Dye-sensitized solar cells (DSSC) are characterized by the fact that electrolytes can be used, raw materials and manufacturing costs are low, and that they have decorative properties for the use of dyes. In recent years, active research has been conducted. . In general, a dye-sensitized solar cell includes a substrate on which a conductive film is formed, a dye-sensitized semiconductor layer in which a semiconductor fine particle film (such as a TiO ₂ film) formed on the substrate and a dye are combined, It consists of a charge transport agent such as iodine and a counter electrode.

  For example, the following techniques have been proposed as surface treatment methods for semiconductor fine particle films for improving the characteristics of dye-sensitized solar cells.

  For example, in Patent Document 1, after applying an oxide semiconductor paste onto a substrate and baking it, a porous layer made of an oxide semiconductor electrode material is obtained, and then the porous layer is chlorinated with a concentration of 1% by weight. A surface treatment for immersing in a titanium (III) solution is performed. After the surface treatment, it is dried and then baked at 450 ° C. for 30 minutes in the air.

  For example, in Patent Document 2, a slurry liquid containing ITO particles is applied on a conductive glass substrate, and after drying, the obtained dried product is baked in air at 500 ° C. for 30 minutes to form a porous ITO film on the substrate. And then the porous ITO film is immersed in water containing 2.0 g / l of fluorotitanium ammonium and 1.2 g / l of boric acid together with the substrate and left at 25 ° C. for 3 hours. Surface treatment by is performed.

For example, Patent Document 3, after coating the SnO ₂ paste containing SnO ₂ fine particles on the substrate, in the air, by performing the baking for 60 minutes at 500 ° C., after obtaining a porous SnO ₂ layer on the substrate, zirconium Surface treatment is performed by immersing in a 4 wt% ethanol solution of tetraisopropoxide for 24 hours. After the surface treatment, the substrate is washed with ethanol and then baked in air at 550 ° C. for 60 minutes.

  For example, in Patent Document 4, after applying a coating liquid for forming a semiconductor film on a transparent glass substrate and performing natural drying or the like to obtain a titanium oxide semiconductor film, 5 g of t-butoxyaluminum is added to t-butyl. Surface treatment is performed by immersing in a solution dissolved in 50 cc of alcohol for 1 hour. After the surface treatment, baking is performed at 450 ° C. for 2 hours.

For example, in Patent Document 5, after a TiO ₂ coating layer is formed on a TiO ₂ porous film, a glass substrate on which the TiO ₂ coating layer is formed is placed in a zinc acetylacetonate ethanol solution having a concentration of 20 mmol / l at room temperature ( The surface treatment is performed by immersion at 25 ° C. for 1 hour. After the surface treatment, baking is performed at 450 ° C. for 30 minutes.

For example, in Patent Document 6, the surface of a porous TiO ₂ thin film is coated with SiO ₂ that is an oxide insulator by using a sputtering method that is a kind of vapor phase film forming method.

JP 2000-1113913 A JP 2001-345125 A Japanese Patent Laid-Open No. 2002-100418 JP 2003-308991 A JP 2004-95387 A JP-A-2005-79068

  In Patent Documents 1 to 5, the photoelectric conversion efficiency is improved by the surface treatment of the semiconductor fine particle film. However, in Patent Document 1 to Patent Document 5, it is necessary to immerse for a long time (for example, several hours or more) and to bake at a high temperature in the surface treatment.

  Accordingly, an object of the present technology is to provide a dye-sensitized photoelectric conversion element and a method for manufacturing the dye-sensitized photoelectric conversion element that can improve photoelectric conversion efficiency and can be manufactured even at low temperature baking.

  In order to solve the above-described problem, the first technique is a dye-sensitized semiconductor electrode layer disposed on a support, a counter electrode, and an electrolyte layer disposed between the dye-sensitized semiconductor electrode layer and the counter electrode. The dye-sensitized semiconductor electrode layer includes metal oxide semiconductor fine particles and an insulating layer that covers at least part of the surface of the metal oxide semiconductor fine particles, and the insulating layer has an amorphous phase at least partially. It is a dye-sensitized photoelectric conversion element containing the metal oxide which has.

  In the second technique, a metal oxide semiconductor fine particle layer is formed on a support, and the metal oxide semiconductor fine particle layer is immersed in a surface treatment solution in which a metal alkoxide is dissolved in an organic solvent, and then fired at a predetermined temperature. Thus, there is provided a method for producing a dye-sensitized photoelectric conversion element comprising a step of forming an insulating layer containing a metal oxide having an amorphous phase at least partially on the surface of metal oxide semiconductor fine particles.

  In the first technique and the second technique, an insulating layer containing a metal oxide having an amorphous phase at least partially is formed on the surface of the metal oxide semiconductor fine particles, thereby increasing the amount of dye adsorption. Can do. Thereby, photoelectric conversion efficiency can be improved.

  According to the present technology, it is possible to provide a dye-sensitized photoelectric conversion element that can improve photoelectric conversion efficiency and can be manufactured even by low-temperature baking, and a method for manufacturing the dye-sensitized photoelectric conversion element.

It is sectional drawing of the principal part of the dye-sensitized photoelectric conversion element by 1st Embodiment of this technique. It is a graph which shows the IPCE curve of Example 1-1 to Example 1-2 and Comparative Example 1. It is a graph which shows the result of the reverse current measurement of Example 1-1 to Example 1-2 and Comparative Example 1. It is a graph which shows the XMA spectrum of Example 1-1. It is a TEM image of the semiconductor layer of Example 1-1.

Hereinafter, embodiments of the present technology will be described with reference to the drawings. The description will be given in the following order.
1. First Embodiment (Configuration Example of Dye-sensitized Photoelectric Conversion Element)
2. Other embodiment (modification)

1. First Embodiment A dye-sensitized photoelectric conversion element according to a first embodiment of the present technology will be described. As shown in FIG. 1, in this dye-sensitized photoelectric conversion element, a dye-sensitized semiconductor layer 2 is formed on a transparent conductive substrate 1, and a conductive substrate 3 whose surface constitutes a counter electrode at least. However, the dye-sensitized semiconductor layer 2 and the conductive substrate 3 are arranged so as to face each other at a predetermined interval, and the electrolyte layer 4 is sealed in a space between them. As the dye-sensitized semiconductor layer 2, a semiconductor fine particle layer having a dye supported thereon is used. The electrolyte layer 4 may be sealed with a predetermined sealing member (not shown).

(Transparent conductive substrate)
The dye-sensitized semiconductor layer 2 is typically provided on the transparent conductive substrate 1. The transparent conductive substrate 1 may be a transparent conductive substrate formed on a conductive or non-conductive transparent support substrate, or may be a conductive transparent support substrate as a whole. The material in particular of this transparent support substrate is not restrict | limited, A various base material can be used if it is transparent.

  The transparent support substrate is preferably one that is excellent in moisture and gas barrier properties, solvent resistance, weather resistance, and the like that enter from the outside of the dye-sensitized photoelectric conversion element, specifically, quartz, sapphire, glass, and the like. Transparent inorganic substrate, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride, tetraacetylcellulose, brominated phenoxy, aramids, polyimides, polystyrenes, polyarylates, polysulfone And transparent plastic resin substrates such as polyolefins. Among these, it is preferable to use a substrate having a particularly high transmittance in the visible light region, but is not limited thereto.

  As this transparent support substrate, it is preferable to use a transparent plastic resin substrate or the like in consideration of processability, lightness and the like. When the transparent support substrate is a transparent plastic resin substrate or the like, it is more preferable because the feature of the surface treatment of the present technology that exhibits the effect of improving the photoelectric conversion efficiency by low-temperature baking is best utilized. The thickness of the transparent support substrate is not particularly limited, and can be freely selected depending on the light transmittance, the shielding property between the inside and outside of the dye-sensitized photoelectric conversion element, and the like.

The surface resistance (sheet resistance) of the transparent conductive substrate 1 is preferably as low as possible. Specifically, the surface resistance of the transparent conductive substrate 1 is preferably 500Ω / □ or less, and more preferably 100Ω / □. When a transparent conductive film is formed on a transparent support substrate, a known material can be used as the transparent conductive film. Specifically, indium-tin composite oxide (ITO), fluorine-doped SnO ₂ ( FTO), antimony-doped SnO ₂ (ATO), SnO ₂ , ZnO, indium-zinc composite oxide (IZO), and the like, but are not limited to these, and two or more of these are used in combination. You can also. Further, for the purpose of reducing the surface resistance of the transparent conductive substrate 1 and improving the current collection efficiency, a wiring made of a conductive material such as a highly conductive metal or carbon is separately provided on the transparent conductive substrate 1. Also good. Although there is no restriction | limiting in particular in the electrically conductive material used for this wiring, It is desirable that corrosion resistance and oxidation resistance are high, and the leakage current of electrically conductive material itself is low. However, even a conductive material having low corrosion resistance can be used by separately providing a protective layer made of a metal oxide or the like. Further, for the purpose of protecting the wiring from corrosion or the like, the wiring is preferably installed between the transparent conductive substrate 1 and the protective layer.

(Dye-sensitized semiconductor layer)
As the dye-sensitized semiconductor layer 2, a porous film obtained by sintering semiconductor fine particles is typically used, and the dye is adsorbed on the surface of the semiconductor fine particles. As a material for the semiconductor fine particles, various compound semiconductors, compounds having a perovskite structure, and the like can be used in addition to elemental semiconductors represented by silicon. These semiconductors are preferably n-type semiconductors in which conduction band electrons become carriers under photoexcitation and give an anode current. Specifically, these semiconductors are TiO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ , TiSrO ₃ , SnO _2, etc. Among them, anatase type TiO ₂ is particularly preferable. The types of semiconductors are not limited to these, and two or more of these can be mixed and used. Furthermore, the semiconductor fine particles can take various forms such as particles, tubes, rods, needles, and the like as required.

  Although there is no restriction | limiting in particular in the particle size of semiconductor fine particle, 1 nm or more and 200 nm or less are preferable at the average particle diameter of a primary particle, Especially preferably, they are 5 nm or more and 100 nm or less. It is also possible to improve the quantum yield by mixing semiconductor fine particles having an average particle size larger than the average particle size into semiconductor fine particles having an average particle size and scattering incident light by the semiconductor fine particles having a large average particle size. is there. In this case, the average particle diameter of the semiconductor fine particles to be mixed separately is preferably 20 nm or more and 500 nm or less.

  The semiconductor layer made of semiconductor fine particles, in other words, the semiconductor fine particle layer, preferably has a large surface area so that a large amount of sensitizing dye can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the support is preferably 10 times or more, more preferably 100 times or more the projected area. The upper limit is not particularly limited, but is usually about 1000 times. In general, as the thickness of the semiconductor fine particle layer increases, the amount of the supported dye increases per unit projected area and thus the light capture rate increases. However, the diffusion distance of injected electrons increases and the loss due to charge recombination also increases. . Therefore, a preferable thickness exists in the semiconductor fine particle layer, but the thickness is generally 0.1 μm or more and 100 μm or less, more preferably 1 μm or more and 50 μm or less, and more preferably 3 μm or more and 30 μm or less. Is particularly preferred.

(Insulating layer)
By performing the surface treatment described later, an insulating layer is formed on the surface of the semiconductor fine particles. The insulating layer may be formed on a part of the surface of the semiconductor fine particles, or may be formed on the entire surface of the semiconductor fine particles. Thereby, the pigment | dye amount adsorb | sucked to a semiconductor layer can be increased compared with the thing which is not performing surface treatment. Therefore, the photoelectric conversion efficiency of the dye-sensitized photoelectric conversion element can be improved.

  The insulating layer includes a metal oxide having an amorphous phase at least partially. Examples of the metal oxide include niobium, zinc, and aluminum oxides. In addition to these, the metal oxide may be an oxide of one or more metals in which a metal alkoxide is present. Typically, for example, oxides such as tin, zirconium, strontium, magnesium, sodium, iron and the like can be mentioned. The film thickness is preferably set to a film thickness through which a tunnel current flows, for example. The film thickness at which the tunnel effect appears and the tunnel current flows differs depending on the metal oxide material and crystallinity, but is typically several nm or less, for example. In addition, it is preferable that an organic substance remains in the insulating layer.

  Here, in order to facilitate understanding of the present technology, the differences between the cited document 1 to the cited document 6 illustrated in the column of [Background Technology] and the present technology are particularly noted. The insulation layers according to the conventional techniques described in the cited documents 1 to 6 are designed to improve the photoelectric conversion efficiency by preventing reverse electrons. In order to prevent reverse electrons, an insulating layer with high crystallinity is necessary. Therefore, it is considered that an insulating layer formed by conventional surface treatment has high crystallinity. On the other hand, the insulating layer formed by the surface treatment of the present technology is amorphous and preferably the organic component remains in the insulating layer. It is considered that the insulating layer of the present technology can increase the adsorption amount of the dye. For example, since the insulating layer of the present technology is thought to contain a large amount of hydroxyl groups and the like that promote the adsorption of the dye, the amount of the dye adsorbed can be increased. In Cited Document 1 and Cited Documents 3 to 5, high-temperature baking is performed, but the present technology is also different in that the insulating layer is made amorphous by baking at low temperature.

  The dye to be carried on the semiconductor layer is not particularly limited as long as it exhibits a sensitizing action. For example, xanthene dyes such as rhodamine B, rose bengal, eosin and erythrosine; Dyes, basic dyes such as phenosafranine, fog blue, thiocin and methylene blue, and porphyrin compounds such as chlorophyll, zinc porphyrin and magnesium porphyrin, and others include azo dyes, phthalocyanine compounds, coumarin compounds, Ru Bipyridine complex compounds, Ru terpyridine complex compounds, anthraquinone dyes, polycyclic quinone dyes, squarylium and the like can be mentioned. Among these, Ru bipyridine complex compounds are particularly preferable because of their high quantum yield. However, the sensitizing dyes are not limited to these, and two or more kinds of these sensitizing dyes may be mixed and used.

(Electrolytes)
The electrolyte may be a combination of iodine (I ₂ ) and metal iodide or organic iodide, bromine (Br ₂ ) and metal bromide or organic bromide, ferrocyanate / ferricyanate, ferrocene / ferricene. It is possible to use metal complexes such as sinium ions, sodium polysulfide, sulfur compounds such as alkyl thiol / alkyl disulfide, viologen dyes, hydroquinone / quinone, and the like. Lithium, Na, K, Mg, Ca, Cs and the like are preferable as the cation of the metal compound, and quaternary ammonium compounds such as tetraalkylammonium, pyridinium, and imidazolium are preferable as the cation of the organic compound. It is not limited, and two or more of these can be mixed and used. Among this, I ₂ and LiI, NaI and imidazolium iodide electrolyte obtained by combining the quaternary ammonium compound such as id are preferred. The concentration of the electrolyte salt is preferably 0.05 mol / l or more and 5 mol / l or less, more preferably 0.2 mol / l or more and 3 mol / l or less with respect to the solvent. The concentration of I ₂ or Br ₂ is preferably 0.0005 mol / l or more and 1 mol / l or less, and more preferably 0.001 mol / l or more and 0.3 mol / l or less.

  Water, alcohols, ethers, esters, carbonate esters, lactones, carboxylic acid esters, phosphoric acid triesters, heterocyclic compounds, nitriles, ketones, amides as a solvent constituting the electrolyte composition Nitromethane, halogenated hydrocarbons, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, hydrocarbons, etc., but are not limited thereto, Moreover, these can also be used in mixture of 2 or more types. Furthermore, an ionic liquid of a tetraalkyl, pyridinium, or imidazolium quaternary ammonium salt can be used as the solvent.

  In order to reduce leakage of dye-sensitized photoelectric conversion elements and volatilization of electrolytes, in addition to dissolving gelling agents, polymers, crosslinking monomers, etc. in the above electrolyte composition, inorganic ceramic particles are dispersed and used as a gel electrolyte It is also possible to do. The ratio of the gel matrix to the electrolyte composition is such that the more the electrolyte composition, the higher the ionic conductivity, but the mechanical strength decreases. Conversely, if the electrolyte composition is too small, the mechanical strength increases but the ionic conductivity. Therefore, the electrolyte composition is desirably 50% by mass or more and 99% by mass or less of the gel electrolyte, and more preferably 80% by mass or more and 97% by mass or less. It is also possible to realize an all-solid-state dye-sensitized photoelectric conversion element by dissolving the electrolyte and plasticizer in a polymer and volatilizing and removing the plasticizer.

(Counter electrode)
As the counter electrode disposed on the surface of the conductive substrate 3, any material can be used as long as it is a conductive material. However, even an insulating material has a conductive property on the side facing the dye-sensitized semiconductor layer 2. This can also be used if a catalyst layer is provided. However, as the counter electrode material, it is preferable to use an electrochemically stable material. Specifically, platinum, gold, carbon, a conductive polymer, or the like is preferably used. For the purpose of improving the catalytic effect of redox, it is preferable that the side facing the dye-sensitized semiconductor layer has a fine structure and an increased surface area. If so, it is desirable that it is in a porous state. The platinum black state can be formed by a method of anodic oxidation of platinum, a reduction treatment of a platinum compound, or the like, and the porous carbon can be formed by a method such as sintering of carbon fine particles or baking of an organic polymer. As the support substrate on which the counter electrode is disposed, the above-described transparent support substrate may be used. In addition, the transparent conductive substrate 1 is used as the conductive substrate 3, and a metal having a high oxidation-reduction catalytic effect such as platinum is wired on the transparent conductive substrate 1, or the surface is made transparent by reducing a platinum compound. It can also be used as a counter electrode.

(Method for producing dye-sensitized photoelectric conversion element)
A method for producing the above-described dye-sensitized photoelectric conversion element will be described.

(Formation of semiconductor fine particle layer)
A semiconductor fine particle layer is formed on the transparent conductive substrate 1. First, a paste in which a semiconductor fine particle layer is dispersed is applied to a predetermined gap (thickness). Specifically, for example, a method in which a paste in which semiconductor fine particle powder or sol is uniformly dispersed in a solvent such as water or an organic solvent is prepared and applied onto the transparent conductive substrate 1 is preferable. Coating is not particularly limited in its method and can be performed according to a known method, for example, dipping method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, As the wet printing method, for example, various methods such as letterpress, offset, gravure, intaglio, rubber plate, and screen printing can be used. After applying the semiconductor fine particle paste, it is preferable to sinter the semiconductor fine particles electronically so as to improve film strength and adhesion to the substrate.

(surface treatment)
(Surface treatment solution)
The surface treatment solution is prepared, for example, by dissolving a metal alkoxide as a solute in an organic solvent.

(Metal alkoxide)
Examples of the metal alkoxide include niobium such as niobium ethoxide, tertiary aluminum butoxide, and zinc methoxyethoxide, and aluminum or zinc metal alkoxide. In addition to these, any metal alkoxide can be used without limitation. For example, as the metal alkoxide, general metal alkoxides such as tin, zirconium, strontium, magnesium, sodium, and iron may be used.

(solvent)
As the solvent, various organic solvents that can dissolve the metal alkoxide can be used. Examples of such an organic solvent include alcohols such as n-butanol and isopropyl alcohol (IPA), and ethanols such as 2-methoxyethanol. In addition to these, any solvent can be used as long as the metal alkoxide is soluble.

(Concentration of metal alkoxide)
The concentration of the metal alkoxide is not particularly limited, but in order to obtain a more excellent photoelectric conversion efficiency improvement effect, it is preferable to set the concentration range so that the insulating layer to be formed does not become too thick. For example, the concentration of the metal alkoxide is preferably greater than 0 mmol / l and 0.5 mmol / l or less, but the concentration of the metal alkoxide is not limited to this range.

(surface treatment)
Next, the semiconductor fine particle layer is immersed in the surface treatment solution. The immersion time is not particularly limited as long as the solution concentration does not change and the environment does not allow impurities to enter.

(Baking)
Next, the semiconductor fine particle layer is fired by heating. The firing temperature is typically set to 150 ° C. or lower, for example.

(Dye adsorption)
Next, the transparent conductive substrate 1 on which the semiconductor fine particle layer is formed is immersed in a dye solution containing a dye, and the dye is adsorbed to the semiconductor fine particle layer.

  The dye supported on the semiconductor fine particle layer is not particularly limited as long as it exhibits a sensitizing action. Basic dyes such as cyanine dyes, phenosafranine, fog blue, thiocin, methylene blue, and porphyrin compounds such as chlorophyll, zinc porphyrin, magnesium porphyrin, and others include azo dyes, phthalocyanine compounds, coumarin compounds, Examples include Ru bipyridine complex compounds, Ru terpyridine complex compounds, anthraquinone dyes, polycyclic quinone dyes, squarylium, and the like. Among these, Ru bipyridine complex compounds are particularly preferable because of their high quantum yield. However, the sensitizing dyes are not limited to these, and two or more kinds of these sensitizing dyes may be mixed and used.

  The method for adsorbing the dye to the semiconductor fine particle layer is not particularly limited, but the sensitizing dye may be, for example, alcohols, nitriles, nitromethane, halogenated hydrocarbons, ethers, dimethyl sulfoxide, amides, N-methylpyrrolidone, Dissolve in a solvent such as 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters, carbonates, ketones, hydrocarbons, water, etc. Or can be applied on the layer. In addition, when a dye having high acidity is used, deoxycholic acid or the like may be added for the purpose of reducing association between the dye molecules.

  After adsorbing the sensitizing dye, the surface of the semiconductor fine particle layer may be treated with amines for the purpose of promoting the removal of the excessively adsorbed sensitizing dye. Examples of amines include pyridine, 4-tert-butylpyridine, polyvinylpyridine and the like. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.

(Electrolyte filling, etc.)
On the other hand, a conductive substrate 3 on which a counter electrode is formed is separately prepared, and the transparent conductive substrate 1 and the conductive substrate 3 are separated from each other by a predetermined distance between the semiconductor fine particle layer and the counter electrode, for example, 1 μm or more and 100 μm or less, preferably Are arranged so as to be opposed to each other with an interval of 1 μm or more and 50 μm or less, and a space for enclosing the electrolyte layer is created using a predetermined sealing member, and the electrolyte is introduced from a pre-formed injection port in this space inject. Thereafter, the liquid injection port is closed. Thus, a dye-sensitized photoelectric conversion element is manufactured.

  According to the method for producing a dye-sensitized photoelectric conversion element of the present technology, a semiconductor fine particle layer capable of improving photoelectric conversion efficiency can be produced by low-temperature firing. As a result, energy consumption in the manufacturing process can be suppressed, and a material having poor heat resistance, such as a plastic resin substrate such as a lightweight, inexpensive, and flexible plastic film, can be used for the support. In addition, the roll-to-roll process can be manufactured at a lower cost with higher productivity. Further, the surface treatment process of the semiconductor fine particle layer can be performed by a simple series of steps of immersing in a metal alkoxide solution at room temperature for a short time, followed by natural drying, and firing at a low temperature (for example, 150 ° C. or less).

  Examples of the dye-sensitized photoelectric conversion element of the present technology will be described.

<Example 1-1>
A transparent conductive substrate was prepared as follows. An FTO substrate (sheet resistance 10Ω / □) made of Nippon Sheet Glass is processed into a size of 15 mm x 25 mm x t (thickness) 1.1 mm, and then used in order with acetone, alcohol, alkaline cleaning liquid, and ultrapure water. Ultrasonic cleaning was performed and the product was sufficiently dried.

(Preparation of the first paint)
P25 (manufactured by Nippon Aerosil Co., Ltd., titania particles, particle size 21 nm) was added to ethanol (solid content 30% by mass), zirconia beads (φ0.65 mm) were further added, and agitator treatment was performed for 24 hours. Was made.
TA300 (manufactured by Fuji Titanium, titania particles, particle size 390 nm) is added to ethanol (solid content 20% by mass), zirconia beads (φ0.65 mm) are further added, and an agitator treatment is performed for 24 hours. Was made.
FTL300 (manufactured by Ishihara Sangyo Co., Ltd., needle-like titania particles / major diameter 5.15 μm) was added to ethanol (solid content 20% by mass), zirconia beads (φ0.65 mm) were further added, and an agitator treatment was performed for 24 hours. An ethanol dispersion was prepared.

  Next, the 1st titania coating material was produced as follows. P25 ethanol dispersion, TA300 ethanol dispersion, FTL300 ethanol dispersion were added respectively, ethanol and buticello were added (mass ratio 95: 5), DBT (butyl titanate dimer, Nippon Soda Co., Ltd., B2 type, http : //Www.nippon-soda.co.jp/tbt-n/derivative.html # B2), and then shaken by hand to complete the first titania paint (solid content 20% by mass). It was. The composition (mass ratio) of the P25 ethanol dispersion, TA300 ethanol dispersion, FTL300 ethanol dispersion, and DBT was adjusted to 52.5: 26.25: 8.75: 12.5, respectively.

(surface treatment)
The first titania paint produced by the above procedure was applied on the substrate with a film thickness of 8 μm using a coil bar (# 44), and after natural drying, baked at 150 ° C. for 30 minutes to form a titania film.

  Next, a niobium ethoxide solution (concentration 0.5 mmol / l) in which niobium ethoxide as a solute was dissolved in n-butanol as a solvent was prepared as a surface treatment solution. In the preparation of the surface treatment solution, the solute and the solvent were mixed with a paint shaker for 30 minutes and then subjected to a filter treatment.

The titania film was immersed in this surface treatment solution for 10 minutes. Then, after air-drying, it baked with the hotplate on air | atmosphere on 150 degreeC and the conditions for 30 minutes. As described above, a titania film (TiO ₂ sintered body) subjected to surface treatment for forming an insulating layer containing niobium oxide was completed.

(Preparation of dye solution)
0.5 mmol / l cis-bis (isothiocyanate) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II) ditetrabutylammonium salt (N719 dye) The TiO ₂ sintered body was immersed in a mixed solvent of tert-butyl alcohol / acetonitrile (volume ratio of 1: 1) at room temperature for 48 hours to carry the dye. This TiO ₂ sintered body was washed with acetonitrile and dried in the dark to complete a dye-sensitized TiO ₂ sintered body.

(Preparation of electrolyte)
An electrolyte solution having the following composition (as described in Adv. Mater. 2003, 15, No. 24, December 17 P2101) was prepared.
1-propyl-3-methylimidazolium iodide: 0.6 mol / l
N-methylbenzimidazole: 0.5 mol / l
I ₂ in3-methoxypropionitrile: 0.1 mol / l

  On the other hand, a counter electrode was prepared by previously forming a Pt film on a FTO glass substrate by sputtering. Next, the two substrates were placed so that the titania film and the Pt film face each other, and bonded together via a silicon spacer having a thickness of 50 μm. Next, the above electrolytic solution was introduced into the element to obtain a dye-sensitized photoelectric conversion element.

<Example 1-2>
Example 1 except that a tertiary aluminum butoxide solution (concentration 0.5 mmol / l) in which tertiary aluminum butoxide was dissolved in IPA (isopropyl alcohol) was used as the surface treatment solution instead of the niobium ethoxide solution. In the same manner as in Example 1, a dye-sensitized photoelectric conversion element was obtained.

<Comparative Example 1>
A dye-sensitized photoelectric conversion element was obtained in the same manner as in Example 1-1 except that the surface treatment was not performed.

(Evaluation)
First, in the dye-sensitized photoelectric conversion elements of Example 1-1 to Example 1-2 and Comparative Example 1, the open circuit voltage (VOC) at the time of irradiation with artificial sunlight (AM1.5G, 100 mW / cm ² ) by a solar simulator. , Short circuit current density (JSC), fill factor (FF), photoelectric conversion efficiency (Eff), and internal resistance (Rs) were measured. The measurement results are shown in Table 1.

  As shown in Table 1, according to the comparison between Examples 1-1 and 1-2 and Comparative Example 1, it was confirmed that the photoelectric conversion efficiency was improved by the surface treatment for forming the insulating layer. did it.

  Next, in order to specify the mechanism of the effect of the surface treatment, in the dye-sensitized photoelectric conversion elements of Example 1-1 to Example 1-2 and Comparative Example 1, IPCE measurement, reverse current measurement (in the dark) The current value at the time of reverse bias was measured), and the amount of the dye adsorbed on the titania film after the dye was supported was measured. The amount of dye was measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy).

  The result of the IPCE measurement is shown in FIG. 2, and the result of the reverse current measurement is shown in FIG. As shown in FIG. 2 and FIG. 3, the IPCE increased by applying the surface treatment, while the reduction of the reverse current was not observed. Further, the amount of adsorbed dye was a niobium-treated sample (Example 1-1) subjected to a surface treatment with a niobium ethoxide solution compared to 100 for an untreated sample (Comparative Example 1) that was not subjected to surface treatment. ) Was 112, and the aluminum-treated sample (Example 1-2) was 103. That is, it was confirmed that the amount of adsorbed dye increased in the samples (Example 1-1 and Example 1-2) subjected to the surface treatment compared to the untreated sample (Comparative Example 1).

(Analysis of insulation layer (surface treatment film))
In order to clarify the physical properties of the surface treatment film, elemental analysis was performed by XMA (X-ray Micro Analyzer). In addition, observation with a TEM (Transmission Electron Microscope), evaluation of crystallinity by XRD (X-ray Diffraction Technique), and measurement of the amount of residual organic matter by thermal analysis were performed. Note that the sample for XRD and thermal analysis is a powder obtained by removing a titania film formed on the glass substrate by the same process as in Example 1-1.

  The results of XMA are shown in FIG. A TEM image of the semiconductor fine particle film of Example 1-1 is shown in FIG. Table 2 shows the measurement results of the amount of residual organic substances by thermal analysis, the evaluation results of crystallinity by XRD, and the presence or absence of metal elements of metal alkoxide in the insulating layer. In addition, about the presence or absence of the metal element about Example 1-2, it is unmeasured.

  As shown by the arrow a in FIG. 4, in Example 1-1, the presence of Nb was confirmed from the result of XMA. In the TEM image shown in FIG. 5, the portion where the lattice image is shown is a titania film, and the surrounding amorphous portion (the portion where the lattice image is not observed) is a niobium oxide layer which is a surface treatment film. It is believed that there is. According to this, the film thickness of the niobium oxide layer is estimated to be around 2 nm. Further, as a result of XRD and thermal analysis, it was shown that the surface treatment film was amorphous containing an organic substance. In the niobium oxide film, there was also a crystal part.

  Considering the above results, the insulating layers of Example 1-1 and Example 1-2 formed by the surface treatment were set at a low firing temperature of 150 ° C., so that the atomic arrangement was at least partially. Since it is amorphous and contains organic matter, it is considered that the “electron barrier band for preventing reverse electrons” shown in the cited reference 1 and the like exemplified in [Background Art] is not formed. This consideration is in agreement with the result (result shown in the graph of FIG. 3) of “the amount of back electrons does not change between the surface-treated sample and the untreated sample”. On the other hand, in Example 1-1 and Example 1-2 in which the surface treatment was performed, the amount of adsorbed dye was increased as compared with Comparative Example 1 in which the surface treatment was not performed, thereby increasing IPCE. It can be concluded as a mechanism for improving photoelectric conversion efficiency.

<Example 2-1>
As the transparent conductive substrate 1, a PEN / ITO film (manufactured by Oike Industry Co., Ltd.) was prepared.

(Preparation of second titania paint)
The second titania paint was produced as follows. Add the above-mentioned P25 ethanol dispersion and TA300 ethanol dispersion, add ethanol and buticello (mass ratio 95: 5), add the above-mentioned DBT, shake by hand, and thereby the second titania paint (Solid content 20 mass%) was completed. The blending mass ratios of P25 ethanol dispersion, TA300 ethanol dispersion, and DBT are 70: 17.5: 12.5, respectively.

  The second titania paint produced by the above procedure is applied on a transparent conductive substrate (PEN / ITO film) with a coil bar (# 44) to a thickness of 8 μm, and after natural drying, baked at 150 ° C. for 30 minutes. Thereby, a titania film was formed.

(surface treatment)
Next, a niobium ethoxide solution (concentration 0.5 mmol / l) in which niobium ethoxide as a solute was dissolved in n-butanol as a solvent was prepared as a surface treatment solution. In the preparation of the surface treatment solution, the solute and the solvent were mixed with a paint shaker for 30 minutes and then subjected to a filter treatment.

  Next, the titania film was dipped in the surface treatment solution for 10 minutes, allowed to dry naturally, and then baked in the air on a hot plate at 150 ° C. for 30 minutes. In this way, a titania film having been subjected to surface treatment for forming an insulating layer was completed.

(Preparation of counter electrode film)
Polyamideimide resin solution (manufactured by Toyobo Co., Ltd., HR11NN (NMP 15 mass% solution)) (P), carbon black (# 2300, manufactured by Mitsubishi Chemical Corporation) (B), NMP, blending ratio P / B = 10, A coating solution was prepared by adding a solid content of 15% by mass, adding φ3 mm zirconia beads 10 times the mass of the solid content, and applying paint shaker stirring (frequency 65 Hz) for 5 hours. This coating solution was applied onto a substrate (SUS316) so as to have a film thickness of 8 μm, and then baked on a hot plate at 150 ° C. for 15 minutes to complete a counter electrode film.

(Preparation of electrolyte)
An electrolyte solution having the following composition (as described in Adv. Mater. 2003, 15, No. 24, December 17 P2101) was prepared.
1-propyl-3-methylimidazolium iodide: 0.6 mol / l
N-methylbenzimidazole: 0.5 mol / l
I ₂ in3-methoxypropionitrile: 0.1 mol / l

<Assembly>
Next, the two substrates were placed so that the titania film and the counter electrode film faced each other, and bonded together via a silicon spacer having a thickness of 50 μm. Next, an electrolytic solution was introduced into the element to obtain a dye-sensitized photoelectric conversion element.

<Example 2-2>
As the surface treatment solution, Example 2-1 except that a zinc methoxyethoxide solution (concentration 0.5 mmol / l) in which zinc methoxyethoxide was dissolved in 2 methoxyethanol was used instead of the niobium ethoxide solution. Similarly, a dye-sensitized photoelectric conversion element was obtained.

<Comparative example 2>
A dye-sensitized photoelectric conversion element was obtained in the same manner as in Example 2-1, except that the surface treatment was not performed.

In the dye-sensitized photoelectric conversion elements of Example 2-1 to Example 2-2 and Comparative Example 2, the open circuit voltage (VOC) and short circuit during irradiation with pseudo sunlight (AM1.5G, 100 mW / cm ² ) by a solar simulator Current density (JSC), fill factor (FF), photoelectric conversion efficiency, photoelectric conversion efficiency (Eff), and internal resistance (Rs) were measured. Table 3 shows the measurement results.

  As shown in Table 3, according to the comparison between Example 2-1 and Example 2-2 and Comparative Example 2, the photoelectric conversion efficiency is improved by performing the surface treatment for forming the insulating layer. I was able to confirm.

2. Other Embodiments The present technology is not limited to the above-described embodiments of the present technology, and various modifications and applications can be made without departing from the gist of the present technology. For example, the numerical values, structures, shapes, materials, raw materials, processes, and the like given in the above-described embodiments and examples are merely examples, and numerical values, structures, shapes, materials, raw materials, processes that are different from these as necessary. Etc. may be used.

  The dye-sensitized photoelectric conversion element can be produced in various shapes depending on the application, and the shape is not particularly limited. The dye-sensitized photoelectric conversion element is most typically configured as a dye-sensitized solar cell. However, the dye-sensitized photoelectric conversion element may be other than a dye-sensitized solar cell, for example, a dye-sensitized photosensor. Electronic devices may be basically any type, including both portable and stationary types, but specific examples include mobile phones, mobile devices, robots, personal computers. , In-vehicle equipment, various household electrical appliances, etc. In this case, the dye-sensitized photoelectric conversion element is, for example, a dye-sensitized solar cell used as a power source for these electronic devices.

DESCRIPTION OF SYMBOLS 1 ... Transparent conductive substrate 2 ... Dye sensitized semiconductor layer 3 ... Conductive substrate 4 ... Electrolyte layer

Claims (8)

A dye-sensitized semiconductor electrode layer disposed on a support;
With the counter electrode,
An electrolyte layer disposed between the dye-sensitized semiconductor electrode layer and the counter electrode;
The dye-sensitized semiconductor electrode layer includes metal oxide semiconductor fine particles and an insulating layer covering at least a part of the surface of the metal oxide semiconductor fine particles,
The above-mentioned insulating layer is a dye-sensitized photoelectric conversion element containing a metal oxide having an amorphous phase at least in part.   The dye-sensitized photoelectric conversion element according to claim 1, wherein the insulating layer further contains an organic substance.   The dye-sensitized photoelectric conversion element according to claim 1, wherein the metal oxide semiconductor fine particles are titanium dioxide fine particles.   The dye-sensitized photoelectric conversion element according to claim 1, wherein the metal oxide is a metal oxide of niobium, aluminum, or zinc.   The dye-sensitized photoelectric conversion element according to claim 1, wherein the support includes a plastic resin substrate.   The dye-sensitized photoelectric conversion element according to claim 5, wherein the support is a plastic resin substrate with a transparent conductive layer. Forming a metal oxide semiconductor fine particle layer containing metal oxide semiconductor fine particles on a support;
The metal oxide semiconductor fine particle layer is immersed in a surface treatment solution in which a metal alkoxide is dissolved in an organic solvent, and then baked at a predetermined temperature, whereby an insulating layer containing a metal oxide having an amorphous phase at least in part is obtained. Forming a dye-sensitized photoelectric conversion element having at least a part of the surface of the metal oxide semiconductor fine particle.   The method for producing a dye-sensitized photoelectric conversion element according to claim 7, wherein the support includes a plastic resin substrate.